Abstract

The uptake of 3H-IgG into human placental chorionic villi in vitro takes place for at least 1 h at 37°C and at 4°C. The rate of uptake is lower at the latter temperature, but still about 20 per cent of the 37°C total. Measurement of cell-associated radioactivity at 4°C cannot therefore be used as a measure of binding: genuine uptake, probably as a result of endocytosis, appears to occur at this temperature. Some proportion of the uptake of IgG at 37°C can be inhibited by colchicine and by cytochalasin B, but some is refractory to these treatments. A coated vesicle-enriched fraction isolated from placenta previously incubated with 3H-IgG was found to be associated with radioisotope.